Pneumatic tires for vehicles adapted to be driven in various areas including desert, wet land, waste land, etc. advantageously have high flexibility, a large ground contact area so as to have sufficient load-carrying capacity and traction for running in such areas and an inflation pressure of about 0.1 to 0.3 kg/cm.sup.2 in order to run at a low ground contact pressure. Accordingly cordless tires made only of rubber or equivalently elastic material and capable of retaining a low pressure are preferable as tubeless pneumatic tires for use in such vehicles.
However, cordless tires are very susceptible to puncture when the tread strikes nails, glass pieces and other sharp obstacles on the road surface. Particularly tubeless pneumatic tires for vehicles to be driven in various areas are more prone to puncture because of varying driving environments.
While pneumatic tires are adapted to mitigate shocks by the deformation of the tread during travel, shock impact, when acting thereon, deforms the tire and also gives the tire an increased inflation pressure, which acts to reduce the deformation and the absorption of the impact.
The reduction in the volume of the deformed portion of the tire due to the deformation is balanced by bulging deformation of another portion of the sealed interior of the tire, or by an increase in the inflation pressure.
As means for rendering tires less susceptible to puncture, tire cords are incorporated in tubeless pneumatic tires which are made entirely of rubber or equivalently elastic material.
With such tubeless pneumatic tires having cords incorporated therein, the cords extend from one bead of the tire to the other bead, with the opposite ends of the cords substantially secured to the beads. The inflation pressure of the tire acts on the cords and is ultimately supported by the beads.
When the tire cords have a low elongation and extend from bead to bead as fixed thereto, the variation in the interior volume of the tire due to deformation is balanced to a greater extent by the increase of the inflation pressure of the tire than by the bulging deformation of the interior of the tire which is restrained by the cords. This greatly reduces the absorption of impact. Although outstanding in endurance against puncture, the tire does not have flexibility sufficient for use in vehicles for travelling in various areas, rendering such vehicles seriously uncomfortable to ride.